Various cardiovascular, neurosurgical, pulmonary, and other interventional procedures, including repair or replacement of aortic, mitral, and other heart valves, repair of septal defects, pulmonary thrombectomy, coronary artery bypass grafting, angioplasty, atherectomy, treatment of aneurysms, electrophysiological mapping and ablation, and neurovascular procedures, may require general anesthesia, cardiopulmonary bypass, and arrest of cardiac function. In order to arrest cardiac function, the heart and coronary blood vessels must be isolated from the remainder of the circulatory system. This serves several purposes. First, such isolation facilitates infusion of cardioplegic fluid into the coronary arteries in order to perfuse the myocardium and thereby paralyze the heart, without allowing the cardioplegic fluid to be distributed elsewhere in the patient's circulatory system. Second, such isolation facilitates the use of a cardiopulmonary bypass system to maintain circulation of oxygenated blood throughout the circulatory system while the heart is stopped, without allowing such blood to reach the coronary arteries, which might resuscitate the heart. Third, in cardiac procedures, such isolation creates a working space into which the flow of blood and other fluids can be controlled or prevented so as to create an optimum surgical environment.
Circulatory isolation of the heart and coronary blood vessels is usually accomplished by placing a mechanical cross-clamp externally on the ascending aorta downstream of the ostia of the coronary arteries, but upstream of the brachiocephalic artery, so as to allow oxygenated blood from the cardiopulmonary bypass system to reach the arms, neck, head, and remainder of the body. Using conventional techniques, the sternum is cut longitudinally (a median sternotomy), providing access between opposing halves of the anterior portion of the rib cage to the heart and other thoracic vessels and organs. Alternatively, a lateral thoracotomy is formed, wherein a large incision is made between two ribs. A portion of one or more ribs may be permanently removed to optimize access. Through this large opening in the chest, a cross-clamp is placed externally on the ascending aorta, thereby isolating the heart and coronary arteries from the remainder of the arterial system. Frequently, the aorta must be dissected away from adjacent tissue to facilitate placement of such a cross-clamp.
To arrest cardiac function, a catheter is introduced through the sternotomy or thoracotomy and inserted through a puncture in the aortic wall into the ascending aorta between the cross-clamp and the aortic valve. Cardioplegic fluid is infused through the catheter into the aortic root and coronary arteries to perfuse the myocardium. An additional catheter may be introduced into the coronary sinus for retrograde perfusion of the myocardium with cardioplegic fluid. In addition, the myocardium is sometimes cooled by irrigation with cold saline solution and/or application of ice or cold packs to the outside of the heart. Cardiac contractions will then cease.
In surgical procedures requiring a median sternotomy or other form of gross thoracotomy, the ascending aorta is accessible by dissection for placement of an external cross-clamp through this large opening in the chest. However, such open-chest surgery often entails weeks of hospitalization and months of recuperation time, in addition to the pain mad trauma suffered by the patient. Moreover, the average mortality rate associated with this type of procedure is about two to fifteen per cent for first-time surgery, and mortality and morbidity are significantly increased for reoperation.
New devices and methods are therefore desired that facilitate the performance of cardiac procedures such as heart valve repair and replacement, coronary artery bypass grafting, and the like, using minimally invasive techniques, eliminating the need for a gross thoracotomy. Such techniques have been described in co-pending application Ser. No. 08/023,778, which is assigned to the assignee of the present invention and am incorporated heroin by reference. In that application methods and devices am described for performing coronary artery bypass grafting, and other procedures through small incisions or cannulae positioned in the chest wall, obviating the need for a gross thoracotomy. One technique described for attesting the heart during such procedures involves the use of a catheter which is introduced into a peripheral artery such as a femoral artery and positioned in the ascending aorta. An expandable member such as an inflatable balloon at the distal end of the catheter is expanded within the ascending aorta to block blood flow therethrough. Cardioplegic fluid may then be infused into the aortic root and into the coronary arteries through a lumen in the catheter, and/or in a retrograde manner through a catheter positioned in the coronary sinus, paralyzing the myocardium.
While this endovascular technique for arresting the heart provides significant advantages over conventional open-chest techniques, in some circumstances the use of an endovascular device for aortic partitioning may be undesirable. For example, in some cases the patient's femoral arteries and other vessels in which such a device could be introduced may not be suitable for such introduction, due to inadequate vessel diameter, vessel stenosis, vascular injury, or other conditions. In addition, where a number of endovascular cannulae are to be introduced to support cardiopulmonary bypass, retroperfusion of cardioplegic fluid, removal of blood from the heart, and other functions, a suitable arterial location for introduction of an endovascular aortic partitioning device may not be available. Further, it may be desirable to minimize the number of arterial punctures so as to reduce the risk of infection and other complications stemming from such punctures.
Methods and devices are therefore needed for isolating the heart and coronary arteries from the remainder of the arterial system and arresting cardiac function that eliminate the need for a gross thoracotomy, but do not rely upon endovascular access into the ascending aorta. The methods and devices should facilitate clamping the ascending aorta between the brachiocephalic artery and the coronary ostia so as to block blood flow therethrough, as well as delivering cardioplegic fluid into the ascending aorta upstream of the clamping location so as to perfuse the myocardium through the coronary arteries.